Experimental studies of perceptual processes, section two Progress report, Jan. - Sep. 30, 1965

Complex discriminative behavior, fixed ratio reinforcement of large units of behavior and deferred reinforcement studied in chimpanzee

Noise and Periodic Modulations in Neural Excitable Media

We have analyzed the interplay between noise and periodic modulations in a mean field model of a neural excitable medium. To this purpose, we have considered two types of modulations; namely, variations of the resistance and oscillations of the threshold. In both cases, stochastic resonance is present, irrespective of if the system is monostable or bistable.Comment: 13 pages, RevTex, 5 PostScript figure

Outcome of infants younger than 1 year with acute lymphoblastic leukemia treated with the interfant-06 protocol: Results from an international phase III randomized study

PURPOSE Infant acute lymphoblastic leukemia (ALL) is characterized by KMT2A (MLL) gene rearrangements and coexpression of myeloid markers. The Interfant-06 study, comprising 18 national and international study groups, tested whether myeloid-style consolidation chemotherapy is superior to lymphoid style, the role of stemcell transplantation (SCT), and which factors had independent prognostic value. MATERIALS AND METHODS Three risk groups were defined: low risk (LR): KMT2A germline; high risk (HR): KMT2A-rearranged and older than 6 months with WBC count 300 3 109/L or more or a poor prednisone response; and medium risk (MR): all other KMT2A-rearranged cases. Patients in the MR and HR groups were randomly assigned to receive the lymphoid course low-dose cytosine arabinoside [araC], 6-mercaptopurine, cyclophosphamide (IB) or experimental myeloid courses, namely araC, daunorubicin, etoposide (ADE) and mitoxantrone, araC, etoposide (MAE). RESULTS A total of 651 infants were included, with 6-year event-free survival (EFS) and overall survival of 46.1% (SE, 2.1) and 58.2% (SE, 2.0). In West European/North American groups, 6-year EFS and overall survival were 49.4% (SE, 2.5) and 62.1% (SE, 2.4), which were 10% to 12% higher than in other countries. The 6-year probability of disease-free survival was comparable for the randomized arms (ADE1MAE 39.3% [SE 4.0; n = 169] v IB 36.8% [SE, 3.9; n = 161]; log-rank P = .47). The 6-year EFS rate of patients in the HR group was 20.9% (SE, 3.4) with the intention to undergo SCT; only 46% of them received SCT, because many had early events. KMT2A rearrangement was the strongest prognostic factor for EFS, followed by age, WBC count, and prednisone response. CONCLUSION Early intensification with postinduction myeloid-type chemotherapy courses did not significantly improve outcome for infant ALL compared with the lymphoid-type course IB. Outcome for infant ALL in Interfant- 06 did not improve compared with that in Interfant-99

Divisive Gain Modulation with Dynamic Stimuli in Integrate-and-Fire Neurons

The modulation of the sensitivity, or gain, of neural responses to input is an important component of neural computation. It has been shown that divisive gain modulation of neural responses can result from a stochastic shunting from balanced (mixed excitation and inhibition) background activity. This gain control scheme was developed and explored with static inputs, where the membrane and spike train statistics were stationary in time. However, input statistics, such as the firing rates of pre-synaptic neurons, are often dynamic, varying on timescales comparable to typical membrane time constants. Using a population density approach for integrate-and-fire neurons with dynamic and temporally rich inputs, we find that the same fluctuation-induced divisive gain modulation is operative for dynamic inputs driving nonequilibrium responses. Moreover, the degree of divisive scaling of the dynamic response is quantitatively the same as the steady-state responses—thus, gain modulation via balanced conductance fluctuations generalizes in a straight-forward way to a dynamic setting

A Dynamic Neural Field Model of Mesoscopic Cortical Activity Captured with Voltage-Sensitive Dye Imaging

A neural field model is presented that captures the essential non-linear characteristics of activity dynamics across several millimeters of visual cortex in response to local flashed and moving stimuli. We account for physiological data obtained by voltage-sensitive dye (VSD) imaging which reports mesoscopic population activity at high spatio-temporal resolution. Stimulation included a single flashed square, a single flashed bar, the line-motion paradigm – for which psychophysical studies showed that flashing a square briefly before a bar produces sensation of illusory motion within the bar – and moving squares controls. We consider a two-layer neural field (NF) model describing an excitatory and an inhibitory layer of neurons as a coupled system of non-linear integro-differential equations. Under the assumption that the aggregated activity of both layers is reflected by VSD imaging, our phenomenological model quantitatively accounts for the observed spatio-temporal activity patterns. Moreover, the model generalizes to novel similar stimuli as it matches activity evoked by moving squares of different speeds. Our results indicate that feedback from higher brain areas is not required to produce motion patterns in the case of the illusory line-motion paradigm. Physiological interpretation of the model suggests that a considerable fraction of the VSD signal may be due to inhibitory activity, supporting the notion that balanced intra-layer cortical interactions between inhibitory and excitatory populations play a major role in shaping dynamic stimulus representations in the early visual cortex

Higher Education and behavior analysis in Europe::Creating a unified approach for the training of autism professionals

Training of behaviour analysts for autism services, has improved notably within a European higher education context. However, regional discrepancies associated with economic, health care, social services, and institutional policies magnify the importance of creating appropriate unified training and consumer protection. Although the European Association for Behaviour Analysis (EABA) has endorsed the Behavior Analyst Certification Board’s (BACB) designations, the absence of European and national regulations, recognition, and accreditation remain significant barriers to quality training and implementation. These challenges are  particularly pertinent in light of BACB decision to limit certification to residents in the USA and Canada after 2022. Advances, challenges, and future directions are discussed within the context of higher education in the United Kingdom, the Czech Republic, Greece, Iceland, Italy, Norway, and Sweden. The post-Bologna European agenda for higher education, globalization and opportunities for the training of behaviour analysts within European higher education are outlined

Adaptive Gain Modulation in V1 Explains Contextual Modifications during Bisection Learning

The neuronal processing of visual stimuli in primary visual cortex (V1) can be modified by perceptual training. Training in bisection discrimination, for instance, changes the contextual interactions in V1 elicited by parallel lines. Before training, two parallel lines inhibit their individual V1-responses. After bisection training, inhibition turns into non-symmetric excitation while performing the bisection task. Yet, the receptive field of the V1 neurons evaluated by a single line does not change during task performance. We present a model of recurrent processing in V1 where the neuronal gain can be modulated by a global attentional signal. Perceptual learning mainly consists in strengthening this attentional signal, leading to a more effective gain modulation. The model reproduces both the psychophysical results on bisection learning and the modified contextual interactions observed in V1 during task performance. It makes several predictions, for instance that imagery training should improve the performance, or that a slight stimulus wiggling can strongly affect the representation in V1 while performing the task. We conclude that strengthening a top-down induced gain increase can explain perceptual learning, and that this top-down signal can modify lateral interactions within V1, without significantly changing the classical receptive field of V1 neurons